Earlier yesterday, U.S. jets struck insurgent targets near the Syrian border, and at least six persons were killed.

Four soldiers from the Army’s Task Force Baghdad died when their patrol struck a roadside bomb in Youssifiyah, 12 miles south of Baghdad in an area known as the “triangle of death.”

Two other soldiers from the 29th Brigade Combat Team also were killed in a bombing yesterday near Balad, 50 miles north of Baghdad. The U.S. military also said a Marine was killed Sunday near Amiriyah, 25 miles west of Baghdad.

Those deaths raised the death toll for October to more than 90, the highest monthly total since January, when 107 American service members died. The latest deaths brought to 2,025 the number of U.S. service members who have died since the Iraq war began in March 2003.

In Washington, Pentagon spokesman Lawrence Di Rita said there is no readily apparent explanation for why the number of U.S. casualties was higher in October than in previous months. But he said the insurgents’ roadside bombs are getting more sophisticated.

“We see an adversary that continues to develop some sophistication on very deadly and increasingly precise standoff-type weapons,” Mr. Di Rita said.

The car bomb in the southern city of Basra exploded at 8:30 p.m. in a commercial district filled with shops and restaurants, killing at least 20 persons and wounding about 40, police said. The restaurants had been packed in the evening with people breaking their fast during the Muslim holy month of Ramadan.

Before dawn yesterday, Marines backed by jets attacked insurgent positions near the Syrian border, destroying two safe houses thought to be used by al Qaeda figures, according to a U.S. statement. It made no mention of casualties, but Associated Press Television News video from the scene showed residents wailing over the bodies of a half-dozen people, including at least three children.

At the local hospital, a doctor said 40 Iraqis, including 12 children, were killed in the attack. The number could not be independently verified.

Iraq’s government has had two important victories in October: a national referendum that adopted a new constitution and the start of the mass-murder trial of Saddam Hussein.

But the insurgents also have been killing coalition forces and Iraqi civilians with roadside and suicide car bombs that seem more powerful and sophisticated than previous ones, based on technology that British officials say apparently originated in neighboring Iran.